Process for preparing improved compositions of lubricating greases



Oct. 8, 1963 IU 1 ,106,532

BC T 3 PROCESS FOR PREPARING IMPROVED COMPOSITIONS OF LUBRICATINGGREASES Filed May 9, 1961 2 Sheets-Sheet l 29 Co(Fe) '40 Bw-unello C/UC1' INVENTOR ATTORNEY Oct. 8, 1963 B. CIUTI 3,106,532

PROCESS FOR PREPARING IMPROVED COMPOSITIONS 0F LUBRICATING GREASES FiledMay 9, 1961 2 Sheets-Sheet 2 Bvunello CI'u-bi INVENTOR ATTORNEY3,19%,53-2 Fatented Oct. 8, 1%63 tree 3,106,532 PROCESS FOR PREPARENGEMPROVED COMPO- SKTIONS OF LUERHCATING GREASES Bruneiio Ciuti, SanDonate Milanese, Italy, assignor to Laboratori Riuniti Studi E RicercheS.p.A., San Donate Milanese, italy, a company of Italy Filed May 1961,Ser. No. 103,896 Claims priority, application Italy May 12, 196i 7Claims. ((31. 25221} It is known that greases based on lithium soaps arenormally employed for lubricating rolling bearings, since they possessspecial characteristics which contribute to impart to said greases greatresistance to mechanical wear, at low temperatures as well as at fairlyelevated temperatures.

There are also known greases based on organophilic bentonites whichpossess particular properties such as to make them unreplaceable forsome kinds of lubrication such as for instance in the case of thelubrication of members which work at temperatures higher than thosewhich greases based on lithium soaps can stand.

Under those conditions in fact greases based on organophilic bentonitesnot only do not melt, but still keep sol-idly bound the lubricatingliquid that constitutes them for the greatest part.

Together with their excellent qualities, lithium greases as well asgreases based on organophilic bentonites present some inconveniences. Itcan be said, for instance, that some types of lithium greases tend toseparate oil, during operation as well as during storage, while withgreases based on organophilic bentonites the main inconvenience isconstituted by a certain difficulty in yielding the oil necessary forlubrication, also apart from the high cost of said organophilicbentonites.

It has also been proposed to prepare greases by mixing in variableproportions a grease based on soaps with an organophilic bentonite(Bentone) grease, to obtain a product wherein the negative properties ofthe two components are eliminated.

However experience has shown that such compositions still presentdeficiencies, such as for instance consider-able losses of grease, to bedetected by the ASTM D l263-53 T test and fairly high values forpenetration. These defects prove mainly obnoxious and in a very markedmanner with bearings for hubs of motor vehicles and generally withbearings subjected to considerable stress for long duration.

It is an object of the present invention to provide a process for thepreparation of an improved composition of lubricating grease.

It has been found in fact that by preparing in one single operation andwith suitable specifications as described hereinafter, greases based onmixtures of lithium soaps and organoph-ilic bentonites, the productsobtained have different characteristics definitely superior as comparedwith those displayed by greases obtained by starting from the same rawmaterials but preparing separately -a lithium soap grease and one basedon organophilic bentonites and then mixing them with each other.

According to the process of the present invention the operatingprocedure is as follows: the organophilic benteonite and lithiumstearate, both conveniently dosed, are incorporated with the mineraloil, heating between 50 and 100 C. if oils having elevated viscosity areinvolved, in such a manner as to obtain a homogeneous mixture free fromnodules, whose consistency may vary according to the kind of oilemployed and to the concentrations of the thickeners; anhydrous methanolis added, acetone and one of the other dispersing agents normallyemployed in the proportion of 1-2% and the mixture is treated in acolloid mill or other analogous apparatus in such a mannet as to obtainmaximum consistency, in relationship to the content of thickeners; themixture is heated slowly under continuous agitation to expel thedispersing agent; heating is continued as well as agitation untilattaining a temperature not lower than 225 C. and not higher than 280 C.On reaching the desired temperature, the grease is poured into a specialcontainer wherein it is cooled down.

By this process a whole series of greases with diiferent percentages oflithium stearate and of Bentone Were prepared and always highly stablegreases were obtained, which were stable during storage as well asduring operation on test hearings in the laboratory and on the road.

In general it can be said that greases so prepared have shown a behaviorin duration and in lubricating quality higher than that of the bestgreases already existing in the trade, in the course of comparativetests carried out on the bearings of the front wheels of motor vehicles.

In the lubricating greases prepared according to the present invention,it has been found that, in addition to the composition, the method ofpreparation is mainly determining, since the latter has influence uponthe intimate structure of the product and, therefore, upon its exploits.

it has also been found that :difierences are noted according to the kindof oil used, and said diiferences are more marked and the grade of thegrease is better, if the oils employed have higher viscosity. In generalthe lubrieating oil employed is an oil having a viscosity higher than 40Engler at 50 C.

The greases prepared by us have, as compared with those of identicalanalytic composition but obtained by mere mixing of a lithium soapgreases with a bentone grease:

(l) Diiierent appearance and colour;

(2) Higher consistency;

(3) Superior adhesion to the bearing.

Observation in the infrared confirms, in a reproducible manner, strictqualitative differences between said greases. Though in fact in thegrease as prepared according to the process of the present inventionthere is not observed the formation of chemical bonds proper, there isnoted a perturbation of the SiO bonds of the Bentone, not observed inthe greases prepared by mere mixing.

X-ray observation permits to establish that the grease preparedaccording to the process of the present invention undergoes a structuralmodification: Bentone 34 in fact presents a structure diiierent fromthat obtainable by mere absorption of the hydro-carbon moleculesconstituting the oil, at low temperature as well as at elevatedtemperature, as commonly found in known greases of the prior art.

The new structure is determined by the interaction of soap with Bentone34.

The greases prepared according to the present invention are finallyadapted to be corrected by additives such as graphite, molybdenumsulfide and other solid lubricants, In general revealing improvedtechnical characteristics. the total content of lithium soap vand oforganophilic ben tonite, with any ratios of the former to the latter,varies from 3 to 20% A series of experiments is reported hereinafter byway of example without limitation.

EXAMPLE 1 The technological tests efl'ected on this grease gave thefollowing results:

Initial Penetration Loss in the penetration, after 100,000 A STM 1203drum. double blows, 53 T test dram.

195 300 nil EXAMPLE 2 A sample of grease having the followingcomposition:

% of Bentone 34 4% of lithium stearate 91% of mineral oil with highviscosity (VE =S3) was prepared operating as in Example 1, varying onlythe temperature, which was brought up to 240 C.

The technological tests gave the following results:

Initial Penetration Loss in the penetration, after 100,000 ASlM 1203-dmrn. double blows, 53 '1 test drnni.

260 330 traces EXAMPLE 3 A sample of grease having the followingcomposition:

2% of Bentone 34 of lithium soap 88% of mineral oil (VE =l6) wasprepared while operating as in Example 1.

The technological tests effected on this grease gave the followingresults:

Initial Penetration Loss in the penetration, after 100,000 ASTM 1263-dinin. double blows, 53 T test,

dninl. percent EXAMPLE 4 A sample of grease having the followingcomposition:

4% of Bentone 34 10% of lithium soap 86% of mineral oil (Vi-3 :7)

was prepared While operating as in Example 1.

The technological tests efiected on this grease gave the Operating as inExample 1, a sample of grease having the following composition wasprepared:

10% of Bentone 34 2% of lithium soap 88% of mineral oil (VE =l6) Thetechnological tests carried out on this grease gave the followingresults:

Initial Penetration Loss in the 5 penetration, after 100,000 xsmr 1203-dmm. double blows, 53 '1 test dmin.

235 313 I absent EXAMPLE 6 Operating as in Example 1, a sample of greasehaving the following composition was prepared:

2% of Bentone 34 3% of lithium soap 95% of mineral oil (VE =7) Thetechnological tests effected on this grease gave the following results:

Initial Penetration Loss in the penetration, after 100,000 ASTM 1263(1mm. double blows, 53 '1 test,

drnrn. percent EXAMPLE 7 30 Greases corrected by additive molybdenumsulfide gave in the technological tests the results reported in thefollowing table:

Table 1 Specific lead pressure Sample Percent of without at max. Type ofadditive seizure, lead withadditive kg. out seizure,

lrg/em.

40 1A 2 115 22, 990 975% Semicolloidal MoSz. 2B 1 21,800 As above. 413 195 20, 570 M08: in

powder form. Ninja corrected by addi- 00 15,600

From this table it will be seen that with the addition of asemicolloidal product definitely better results are obtained with 2% ofadditive, in fact an increase of the seizure load is noted by 25 kg. anda diminution of wears, working be it with medium loads, be it withelevated It will be noted that besides the consistency also thestructure of the two types of grease is considerably different; thesample A appears nearly spinning (while the other one has gelatinousstructure) and resists mechanical Work better. Hence it is possible toconclude that using a high viscosity oil for the preparation of a greasebased on lithium and Bentone, there is obtained a product of a structureparticularly suitable to avoid phenomena of canalization duringoperation on bearings.

EXAMPLE 9 Greases having the following compositions:

(a) 4% of lithium stearate 5% of Bentone 34 91% of high viscosity oil VE=30 (b) 4% of lithium stearate 5% of Bentene 34 91% of low viscosity oilVE =7.5

were prepared in the following manner:

(1) The two samples 1:: and 1b were prepared operating according toprocess known from the prior art, namely by dispersing the stearate in50% of the oil, in the presence of 2% of methyl alcohol, heating up to225 C.

v and cooling rapidly. In the other half of the oil, in the presence of2% of methyl alcohol, there is dispersed Bentone 34; the mixture isground to maximum consistency and the two greases so obtained are mixedand ground at room temperature.

(2) For other two samples 2a and 2b the lithium stearate grease wasprepared as in (1), then the Bentone 34 grease was subjected to heatingup to 225 C., after grinding; after the cooling down to roomtemperature, the two greases were mixed and ground.

(3) Finally the samples 3a and 3b were obtained by mixing lithiumstearate, oil and Bentone 34 in the cold and in the presence of 2% ofmethyl alcohol, grinding the mass obtained and heating it up to 225 C.,cooling then rapidly in a metallic vessel. Subjecting the above citedexamples to tests of mechanical manipulation, the following results wereobtained:

Table 2 From Table 2 there are noted between the greases of types 1 and2 and the greases of type 3, be it utilizing high viscosity oils be itutilizing lower viscosity oils or, differences of characteristics to theentire advantage of greases of type 3, prepared according to the presentinvention, be it in the initial behaviour or be it in that duringlong-lasting tests.

The greases of Example 9 were observed by X-rays. The X-ray diffractionspectra obtained with the difiractometer equipped with Geiger arereported in FIGS. 1 and 1a of the appended drawings (for the samples 1a,2a, 3a and 1b, 2b, 3b respecively).

The spectra are characterized by an intensive and common band due to theoil and by some more or less widened peaks due to the thickener; as canbe observed from the following table, they differentiate two types ofstructure which we shall call at and ,8.

Table 3 Structure 0: Structure ,3 Greases 1 and 2 (a and b) Greases 3 (aand b) d (A) Intensity d (A Intensity observed observed strong 4244Weak. medium medium-weak-.. 14-15 strong.

(1) Though the Bentone 34 has adsorbed, in all of the cases, someorganic fluid bringing the distance of the siliceous layers from 24 A.to 42 A. approximately, the structural distribution or the type of fluidadsorbed are equal for the greases Nos. 1 and 2 (a and b) but differ forthose No. 3 (a and b). During the preparation of the greases of type 3,samples were taken at various conditions of heating: the X-ray spectrareported in FIG. 2 of the appended drawings, show that:

(2) The structure of the on type begins forming with the mere mixing ofthe products;

(3) The passage from the a structure to the B structure begins at about180 C. and is completed at about 220 C.;

(4) At about 180 C. the reflexions of the crystalline stearate disappearowing to the melting of the product which forms an isotropic solutionwith the oil.

The conclusion is that:

(a) The formation of the 5 structure is determined by the soap.

(b) The interaction between soap and Bentone is caused when the former,at elevated temperature, finds itself in solution in the oil: theadsorption of the oil, under these conditions, involves also theintroduction of soap molecules between the Bentone layers.

(c) The presence of polar molecules such as those of the stearatedisturbs the organization of the hydrocarbon molecules constituting theoil by varying the distribution of the electronic density among thesiliceous layers of the Bentone.

These structural modifications are at the basic of the synorgismobserved in the technological properties of the greases of type 3.

I claim: 7

1. A process for preparing improved lubricating greases comprisinglubricating oil, lithium soap and organophilic bentonite, characterizedin that the lithium soap and the organophilic bentonite total content,in any ratio of the former to the latter, varies from 3 to 20%, and inthat the lithium soap and the organophilic bentonite are homogenized inthe lubricating oil and heated to a temperature of between 50 and C.until disappearance of nodules; then mixing with the mixture previouslyobtained a dispersing agent, selected from the group consisting ofalcohols, ketones and esters, in the proportions of 1 to 2%, thentreating the mixture obtained until the maximum possible consistency inrelationship with the content of the thickeners is obtained, expellingthe dispersing agent from the mixture by slow heating and undercontinuous stirring, and continuing heating and stirring until atemperature not lower than 225 C. and not higher than 280 C. isattained, and when that temperature is attained cooling the grease.

2. A process according to claim 1, characterized in that the lubricatingoil employed is an oil having viscosity higher than 0 Engler at 450 C.

3. An improved lubricating grease obtained by the process according toclaim 1.

4. An improved lubricating grease obtained by the process according toclaim 1, and including from about 1% to 2% of a workable solidlubricating grease additive.

5. An improved lubricating grease obtained by the process according toclaim 1, and including from about 1% to 2% of a solid lubricating greaseadditive selected '1? from the "roup consisting of molybdenum sulfide,and graphite.

6. An improved lubricating grease obtained by the process according toclaim 1, and including from about 1% to 2% of a workable liquidlubricating grease dispersing agent.

7. An improved lubricating grease obtained by the process according toclaim 1 and including from about References Cited in the file of thispatent UNITED STATES PATENTS McCarthy June 14, 1955 Sawyer et a1. June27, 1961

1. A PROCESS FOR PREPARING IMPROVED LUBRICATING GREASES COMPRISINGLUBRICATING OIL, LITHIUM SOAP AND ORGANOPHILIC BENTONITE, CHARACTERIZEDIN THAT THE LITHIUM SOAP AND THE ORGANOPHILIC BENTONITE TOTAL CONTENT INANY RATIO OF THE FORMER TO THE LATTER, VARIES FROM 3 TO 20%, AND IN THATTHE LITHIUM SOAP AND THE ORGANOPHILIC BENTONITE ARE HOMOGENIZED IN THELUBRICATING OIL AND HEATED TO A TEMPERATURE OF BETWEEN 50 AND 100*C.UNTIL DISAPPEARANCE OF NODULES; THEN MIXING WITH THE MIXTURE PREVIOUSLYOBTAINED A DISPERSING AGENT, SELECTED FROM THE GROUP CONSISTING OFALCOHOLS, KETONES AND ESTERS, IN THE PROPORTIONS OF 1 TO 2%, THENTREATING THE MIXTURE OBTAINED UNTIL THE MAXIMUM POSSIBLE CONSISTENCY INRELATIONSHIP WITH THE CONTENT OF THE THICKENERS IS OBTAINED EXPELLINGTHE DISPERSING AGENT FROM THE MIXTURE BY SLOW HEATING AND